Non-Patent Document 1 describes a blue laser diode formed on a nonpolar m-plane gallium nitride substrate. The lasing wavelength is 451.8 nm and the threshold current is 134 mA. The laser diode includes an InGaN quantum well structure, a p-type GaN or InGaN optical guiding layer, an n-type GaN or InGaN optical guiding layer, and an Al-containing cladding layer.
Patent Document 1 describes an AlGaInN-based edge emitting semiconductor laser device. The semiconductor laser device is fabricated on a sapphire substrate. A GaInN-ELO structure layer is formed on the sapphire substrate and a stacked layer structure is grown on the structure layer by MOCVD. The stacked layer structure is constituted by an n-GaInN contact layer, an n-AlGaInN cladding layer, an n-GaN optical guiding layer, a GaInN active layer, a p-GaN optical guiding layer, a p-(GaN:Mg/AlGaInN) cladding layer, and a p-GaInN contact layer.
Patent Document 2 describes a light-emitting device employing a sapphire substrate. The light-emitting device includes a first intermediate layer composed of In0.08Ga0.92N, a second intermediate layer composed of In0.15Ga0.85N, and a light-emitting layer composed of In0.20Ga0.80N.
Patent Document 3 describes a group III nitride-based compound semiconductor light-emitting device. This light-emitting device includes an In0.03Ga0.97N intermediate layer, an n-type cladding layer, and a light-emitting layer. The n-type cladding layer is positioned between the intermediate layer and the light-emitting layer. The light-emitting layer includes a GaN barrier layer and an In0.20Ga0.80N well layer.    [Non-Patent Document 1] JJAP, vol. 46, No. 35, 2007, p. L820-L822    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2003-332697    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 9-266327    [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2000-286448